Process and apparatus for breaking foam when treating petroleum or derivatives thereof with alkaline material



s 2,920,036 I I PROCESS AND APPARATUS FOR BREAKING FOAM WHEN TREATINGPETROLEUM R DE- RIVATIVES THEREOF: WITH ALKALINE MA- a:

William A. Gallup, Media, and Hugh L. Myers, Springfield, Pa., assignorsto Sun OilCornpany, Philadelphia,

122., acorporation of New Jerseyl i.

Application April 1s, 1956, Serial b. 519,021 6 Claims. or. 208-284)This invention relates to processa-n'd apparatus for treating petroleumor derivatives thereof with alkaline material, and more particularly toprocess and apparatus for avoiding detrimental effects of foaming insuchtreating. v t It is known in the art to treat various petroleummaterials with alkaline materials such asaqueous caustic soda in orderto refine the petroleum material. In 'one type of process, to' whichthepresent invention is particrefining" zone, either periodically orcontinuously, in

order to maintain the desired alkalinity.

A serious problem which is frequently encountered in refining processesas described above is the formation of objectionable deposits on metalsurfaces in'the refining zone; such deposits frequently result inexcessive pres- Unit W8 sure drop of vapors in passing through therefining zone,

interference with flow of liquid alkaline material through the refiningzone, etc. Another serious problem is the entrainment of liquid alkalinematerial by rising vapors, such entrainment often resulting incontamination of distillate products with alkaline material.

It has been found that a factor contributing to these detrimentalefiects is the formation of foam in the refining zone, as a result oftheintroduction ofw'ate'r thereinto with the fresh alkaline materialwhich is'added in order to maintain alkalinity. The refining operationis generally conducted at a'temperature substantially above the boilingpoint of water, so that' the :water introduced with the alkalinematerialis flashed uponentry into the refining zone. The use ofanhydrous alkaline materials to overcome -this problem is not asatisfactory solution, since anhydrous caustic sodaforexample requires"an expensive and difficult fusion operation and is also difficult'=toconvey satisfactorily inthe molten condition.

The present invention provides a novel manner of handling alkalinematerial containing water or other volatile materials, while avoidingthe detrimental effects which characterize the prior art operation.According; to the present invention, as applied to the system previouslygiven by way of example, the fresh aqueous alkaline material isintroduced into the liquid alkaline material previously in the system,at a location which is external to the refining zone, the introductionbeing performed under condition which result in the production offoam.The

resulting mixture is passed through a foam-breaking constriction inorder to shear the foam, andthen is introduced through an elongatedconduit, which functions as 'to 10 pounds per square inch.

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a defoaming sectionfinto the refining "zone. Operation in this manner iscapable of eliminating foam from the refining zone itself, with theresult'that the deposits and entrainment encountered in conventionaloperation are 're ducedor eliminated. l r t The foam-breakingconstriction which is employed according to the invention can be ofanyjsuitable construc tion to give a pressure drop across theconstriction;within the approximate range from 2 to 30poun'ds per squareinch; Pressure drops within th is range arefirequired for satisfactoryshearing of foam. Pr'eferred pressure drops are those within theapproximate range from 5 to-15 pounds per square inch. .A preferredconstruction for the fo'a'm breakingconstriction is an orifice plateconsisting of a thin transverse" plate in the conduit for conveyance ofalkaline material, the plate containing a circular orifice havingsuitable proportions to provide thejdesired pressure drop; Inthe lightof the present specification, a person skilled in the art can choose theproper'propoiftions for a given operation, in order to provide thedesired pressure drop. I H I In one embodiment of theinvention, fresh'alkaline material is introducedinto liquid alkaline material previ ouslyin the system withthe assistance of suitablefrnixing means,such asan"orificejust'downstreain from the point at which the 'fresh 'alkalinematerial is introduced into the alkaline material previously in thesystem. "Pre ferred pressure drop for such mixing orifice, in ordertoprovide efficient mixing, is within the approximate range'jfrom '5 Theportion of the apparatus between the' locus of vaporization of volatilematter and the ,foam;breaking orifice constitutes a foaming section,wherein 'yolatile matter vaporized fronrthe fresh I alkaline'r'naterialpro duces a foam 'with the" relatively non-volatile liquid alkalinematerial} The residence time 'of the liquid alkaline material in passingthroughthis foaming section 'is preferably within the 'appr'oximaterangefrom 001 to '10 seconds, more preferably 004 to 1.0 second.Longerresidence times, can be employed. if desired, but are gerierallyunnecessary. The residence time should; be at least 0.01 'seco'ndhowever, in order to provide satisfactory operation. I j V 1 i v f Theratio 1 of length to cross-sectional 'area in the foaming section ispreferably such as to be equivalent to a ratio of length to diameterwithin the approximate range from '8 to 100. Longer foaming sectionscan'beemployed if desired, but are. generallyv unnecessary; Preferredratios of length to diameter are those in the approximate range from 30to 60. The ratio should be at least 8. for satisfactory operation.

The foaming section preferably has larger cross-sectional area than thecross-sectional area in the portion of the apparatus. which is directlyupstream therefrom. The use of relatively larger cross-sectional area inthe foaming section avoids, the hammering which may otherwise -occur asa result of foaming in the conduit. v

The portion'of theapparatus between the foambreak .ing orifice and thereceivingzone. into which thealkaline material is ultimately introducedconstitutes a defoaming section in which the suppression of foaminitiated by the foam-breaking orifice is completed. [The-residencetime'of alkaline material inthe'defoaming section. should be'at least0.01 second, in order that the defoaming can be satisfactorily completedbeforeiintroduction of the f the conduit. Generally, it will not benecessary or desirable to employ a conduit whose length is more than 100times its diameter; however, such longer conduits can be employed ifdesired. Preferred ratios of length to diameter are those within theapproximate range from 18m 40. In a conduit having other than circularcross section, the ratios of length to cross-sectional area should .besuch as to provide a ratio equivalent to those set forth above for aconduit having circular cross-sectional area.

In typical operation according to one embodiment of the invention, theliquid alkaline material previously in the system is sufficiently hot atthe time of mixing with the fresh alkaline material to vaporize volatilematter from the latter and form foam. The temperature of the 7 liquidalkaline material may for example be within the approximate range from500 to 750 F. In such cases, it is not necessary to supply heat to themixture of liquid alkaline material and fresh alkaline material, thoughsuch heating can be performed in cases where it is necessary in order tovaporize the volatile matter and form foam. In some cases, volatilematter can be vaporized from liquid alkaline material entirely byindirect heating without admixture with hot alkaline material or otherdirect heating medium.

In operation according to one embodiment of the invention, the refiningzone is commonly maintained at a pressure below atmospheric, for exampleless than 10 p.s;i.a., and often less than p.s.i.a. However, the processand apparatus according to the invention are also applicable in systemsoperating at atmospheric pressure or above.

The invention will be further described with reference to the attacheddrawing, wherein Figure 1 is a schematic diagram of a system accordingto the invention, and Figure 2. illustrates in more detail a portion ofthe apparatus represented in Figure 1.

Referring to Figure 1, a Vacuum distillation tower 10, a mixing orifice11,.and a foam-breaking orifice 12 are illustrated therein, togetherwith appropriate piping for conveyance of the alkaline materials. Inoperation, by way of example, reduced crude petroleum containingnaphthenic acids is introduced through line 13 into vacuum tower 10.Vapors of a portion of the reduced crude pass upwardly through arefining section in tower containing liquid alkaline material introducedthrough line 14. The naphthenic acids in the vapors react with thealkaline material to produce alkali metal naphthenates which becomeincorporated in the liquid alkaline material. The vapors from whichnaphthenic acids have been removed pass into an upper fractionatingsection of tower 10 and are fractionated in conventional manner toobtain distillate s, which are removed as generally indicated by line"15. Residue is removed from the tower 10 through line '16.

The liquid alkaline material passes downwardly from tray to tray withinthe refining zone and is continuously removed from'the tower throughline 17 by means of pump 24. The material removed contains liquid oilwhich has been condensed from the vapors during passage of the latterthrough the refining zone, and also contains alkali metal vnaphthenatesand fresh alkali metal hydroxide. Typical proportions of materials inthe liquid alkaline material removed through line 17 are: liquid oil, 83.5%; alkali metal naphthenates, 15%; and alkali metal hydroxide, 1.5%.

' A portion of the liquid alkaline material withdrawn through line 17 ispassed through line 18 to suitable means for recovering naphthenic acidsfrom the liquid alkaline material. The remainder is passed throughcontrol valve 19 and then through mixing orifice 11. The purpose of'valve 19 is to regulate the flow rate of liquid alkaline ma- ,terialthrough line 17 and the other conduits through which liquid alkalinematerial passes before re-introduc- 91 to Wa 1 Fresh queous caust c sodas in roduced through line of the alkaline material through foam-breakingorifice 12, and the defoaming is completed during passage of thealkaline material through line 22 which constitutes a defoaming section.Valve 23 in conduit 22 is an emergency valve which in ordinary operationis fully open.

The length and volume of foaming section 21 and of defoaming section 22should be sufliciently great, as previously specified, to providesatisfactory operation with regard to formation of foam and subsequentsuppression thereof. If the foaming section does not provide sulficientresidence time, the foam is not fully formed when it reaches thefoam-breaking orifice, and the effectiveness of the latter issubstantially impaired, with the result that foam may be formed afterpassage through the orifice 12, and introduced into tower v10 withdetrimental results. If the defoaming section is not sufiiciently long,in relation to the cross-sectional area thereof, the defoaming initiatedby orifice '12 is not completed before introduction of alkaline materialinto tower 10, and foaming in the latter results. I

Referring to Figure 2, the conduit 17, the conduit 20 and the orificeplate 11 are illustrated in somewhat greater detail. As shown therein,the outlet of conduit 20 is positioned quite close to the orifice 24, inorifice plate ,11, the distance being for example about one inch, in thecasewhere a 1.5 inch diameter orifice, a line 17 having diameter of 4 to6 inches, and a line 20 having diameter of one inch are employed. Withthis construction, highly efiicient mixing of caustic soda introducedthrough line 20 with liquid alkaline material previously in the system,passing through line 17, is obtained.

The following examples illustrate the invention:

Example I Operation conforming generally to that illustrated in thedrawing was carried out, liquid alkaline material at a temperature inexcess of 500 F. being withdrawn through line 17 having diameter of /2inch, at a rate of 2700 cc. per minute. The mixing orifice had adiameter of /8 inch. Aqueous caustic soda (50 B.) was introduced throughline 20 at a rate of 38 cc. per minute. The foaming section consisted of8.5 inches of /2 inch pipe followed by 17 inches of 1 inch pipe, thusbeing 34 nominal pipe diameters long, and providing a residence time ofabout 0.038 second as subsequently shown. The foambreaking orifice had adiameter of inch. The temperature near the foam-breaking orifice was 550F., and the pressure just upstream from the foam-breaking orifice was 25inches of mercury vacuum (about 5 inches of mercury absolute). Thedefoaming section consisted of 1 inch pipe and had a length of 18inches. The defoaming section discharged the liquid alkaline materialinto a receiving vessel which was maintained under nearly com pletevacuum. In operation as described above, the foam produced in thefoaming section was completely suppressed during passage of the alkalinematerial through the defoaming section, and no foaming occurred in thereceiving vessel.

By way of comparison, similar operation carried out in the absence ofthe foam-breaking orifice results in severe foaming in the receivingvessel.

The manner of calculation of residence time is given elow for thefoaming section in this example, in order to illustrate the calculation:The volume of the foaming section was about 17.24 cubic inches, since itcontained 8.5 inches of Vzinch pipe having cross-sectional area of 0.304square inch and 17 inches of 1 inch pipe having cross-sectional area of0.862 square inch. The caustic soda rate was 38 cc. per minute or about58 grams'per inin'ute sincethe specific gravity of 50 B. caustic soda isabout 1.53; the rate of introduction of water was thus about 29 gramsper minute since 50 B. caustic soda contains about 50 percent water.Assuming complete vaporization of water at 550 F. and 25 inches ofmercury vacuum, the volumetric water vapor rate (the number of moles ofwater multiplied by 22,400 and correction factors for temperature andpressure) was about 441,000

cc. per minute. The volumetric rate of water vapor (441,000) and liquidalkaline material (2700) was thus about 444,000 cc. per minute, or 450cubic inches per second. Division of the foaming section volume by 450gives a residence time of about 0.038 second.

Comparison Example I Operation generally similar to that carried out inExample I, but with the foam-breaking orifice located nearer thereceiving vessel, so that the length of the defoaming section was onlyfour times the diameter thereof, was performed. The conditions were thesame as those in Example I with the following exceptions: caustic rate,40 cc. per minute, temperature and pressure near the foam-breakingorifice, 545 F. and 12 p.s.i.g. respectively, residence time in foamingsection, about 0.7 second. The caustic was added to the other alkalinematerial in a mixing valve, rather than an orifice as in Example I. Inthis operation, severe foaming occurred in the receiving vessel.Comparison of these results with those obtained in Example I is given inthe following table:

Ratio of Length to Diameter in Defoaming Section Result Severe foam. Nofoam.

In this example, the residence time in the defoaming section was about0.0073 second, calculated as follows: volume of defoaming section, about3.45 cubic inches; rate of introduction of Water in caustic soda, about30.5 grams per minute; volumetric water rate at 545 F. and about 5inches of mercury absolute pressure (this being the average pressure inthe defoaming section), about 465,000 cc. per minute; volumetric rate ofwater vapor and liquid alkaline material, about 468,000 cc. per minute,or about 475 cubic inches per second; quotient of 3.45 divided by 475,about 0.0073. Thisresidence time was less than that in the defoamingsection of Example I and was insufiicient for satisfactory defoaming.

This example shows that ratio of length to diameter and residence timeare important characteristics of the defoaming section and the operationthereof.

Comparison Example 11 Operation generally similar to that in Example I,but employing in the foaming section a residence time of only about0.007 second, was performed; the defoaming section had ratio of lengthto diameter of 52. The conditions were the same as in Example I with thefollowing exceptions: caustic rate cc. per minute, temperature andpressure near the foam-breaking orifice, 560 F. and 28 inches of mercuryvacuum (about 2 inches of mercury absolute). Caustic addition was as inComparison Example 1. Severe foaming occurred in the receiving vessel.The following table shows a comparison of these results with thoseobtained in Example I.

Result Residence Time in Seconds in Foaming Section N o foam. Severefoam.

These examples showthat' the. residence time in the foamingsection is acritical factor for obtaining satisfactory results according. to theinvention..

In the process according to the invention,.the pressure drop across thefoam-breaking constriction is maintained at a substantially constantlevel within the approximate range from 2 to 30 pounds per square inch.'Some fluctuation of pressure drop is of course permissible, but it isnot feasible to use the foam-breaking constriction as 'a control valve,since the presence of the foam would interfere with such function.Preferably, the foambreaking constriction is provided by an orificeplate which is not adapted to function as a valve.

Although the invention has been described previously with regard tointroduction of aqueous caustic soda into a process for treatment ofpetroleum vapors with liquid alkaline material, it is also applicable toother treatments of petroleum or derivatives. Thus, for example, causticsoda containing sodium sulfide produced in refining petroleum containingH 8 can be admixed with oil-inso1uble sulfonic acids produced insulfonation of petroleum; upon such mixing, the sulfonic acids areneutralized by caustic soda, and concurrently, sodium sulfide reactswith acidic materials to release H 8 to produce a foam. According to theinvention, the mixture is passed through a foaming section, afoam-breaking orifice, and a defoaming section beforeintroduction into areceiving vessel, foaming in the latter thus being avoided.

The invention claimed is:

1. In a petroleum refining process wherein liquid alkaline material iscontacted with hydrocarbons in a refining zone, the liquid alkalinematerial is subsequently removed from the refining zone, an aqueousalkaline material is admixed with the removed liquid alkaline material,the latter being at a temperature suflicient to flash vaporize waterfrom the aqueous alkaline material thereby to form foam, and theresulting mixture is reintroduced into the refining zone, theimprovement which comprises, prior to the reintroduction, passing theresulting mixture through a foaming zone, the residence time in which isat least 0.01 second, subsequently passing the mixture through aconstriction across which the pressure drop is maintained at asubstantially constant level within the approximate range from 2 to 30pounds per square inch, subsequently passing the mixture through adefoaming zone having ratio of length to cross-sectional area equivalentto a ratio of length to diameter of at least 8, the residence time inwhich defoaming zone is at least 0.01 second, and introducing themixture from the defoaming zone into the refining zone.

2. Process according to claim 1 wherein the refining zone is maintainedat a pressure less than 10 p.s.i.a.

3. Process according to claim 1 wherein said temperature is in theapproximate range from 500 to 750 F.

4. In apparatus for refining petroleum which comprises a refiningvessel, means for introducing petroleum into the refining vessel, meansfor removing refined petroleum from the refining vessel, a conduitcommunicating with the refining vessel and adapted to remove liquidalkaline material therefrom, and means for introducing aqueous alkalinematerial into the conduit, the improvement which comprises meansproviding a constricted passageway having fixed cross-sectional areaadapted to produce a pressure drop within the approximate range from 2to 30 pounds per square inch, a second conduitfor conveying the alkalinematerial to said constricted passageway from the point of introductionof aqueous alkaline material, and a third conduit for conveying alkalinematerial from said constricted passageway to said refining vessel, thesecond and third conduits each having a ratio of length tocross-sectional area equivalent to a ratio of length to diameter of atleast 8.

5. Apparatus according to claim 4 wherein said constricted passageway isproyided by an orifice plate.

6. Apparatus according to claim 5, and additionally comprising a secondorifice plate adjacent anddownstream from said means for introducingaqueous alkaline material.

References Cited in'the file of this patent UNITED STATES PATENTSMcCorquodale et all Feb. 11, 1941 Hoover Nov. 3, 1953 Trusty et a1. Oct.23, 1956 Blatz Dec. 11, 1956

1. IN A PETROLEUM REFINING PROCESS WHEREIN LIQUID ALKALINE MATERIAL ISCONTACTED WITH HYDROCARBONS IN A REFINING ZONE, THE LIQUID ALKALINEMATERIAL IS SUBSEQUENTLY REMOVED FROM THE REFINING ZONE, AN AQUEOUSALKALINE MATERIAL IS ADMIXED WITH THE REMOVED LIQUID ALKALINE MATERIAL,THE LATTER BEING AT A TEMPERATURE SUFFICIENT TO FLASH VAPORIZE WATERFROM THE AQUEOUS ALKALINE MATERIAL THEREBY TO FORM FOAM, AND THERESULTING MIXTURE IS REINTRODUCED INTO THE REFINING ZONE, THEIMPROVEMENT WHICH COMPRISES, PRIOR TO THE REINTRODUCTION, PASSING THERESULTING MIXTURE THROUGH A FOAMING ZONE, THE RESIDENCE TIME IN WHICH ISAT LEAST 0.01 SECOND, SUBSEQUENTLY PASSING THE MIXTURE THROUGH ACONSTRICTION ACROSS WHICH THE PRESSURE DROP IS MAINTAINED AT ASUBSTANTIALLY CONSTANT LEVEL WITHIN THE APPROXIMATE RANGE FROM 2 TO 30POUNDS PER SQUARE INCH, SUBSQUENTLY PASSING THE MIXTURE THROUGH ADEFOAMING ZONE HAVING RATIO OF LENGTH TO CROSS-SECTIONAL AREA EQUIVALENTTO A RATIO OF LENGTH TO DIAMETER OF AT LEAST 8, THE RESIDENCE TIME INWHICH DEFOAMING ZONE IS AT LEAST 0.01 SECOND, AND INTRODUCING THEMIXTURE FROM THE DEFOAMING ZONE INTO THE REFINING ZONE.
 4. IN APPARATUSFOR REFINING PETROLEUM WHICH COMPRISES A REFINING VESSEL, MEANS FORINTRODUCING PETROLEUM INTO THE REFINING VESSEL, MEANS FOR REMOVINGREFINED PETROLEUM FROM THE REFINING VESSEL, A CONDUIT COMMUNICATING WIHTTHE REFINING VESSEL AND ADAPTED TO REMOVE LIQUID ALKALINE MATERIALTHEREFROM, AND MEANS FOR INTRODUCING AQUEOUS ALKALINE MATERIAL INTO THECONDUIT, THE IMPROVEMENT WHICH COMPRISES MEANS PROVIDING A CONSTRICTEDPASSAGEWAY HAVING FIXED CROSS-SECTIONAL AREA ADPATED TO PRODUCE APRESURE DROP WITHIN THE APPROXIMATE RANGE FROM 2 TO 30 POUNDS PER SQUAREINCH, A SECOND CONDUIT FOR CONVEYING THE ALKALINE MATERIAL TO SAIDCONSTRICTED PASSAGEWAY FROM THE POINT OF INTRODUCTION OF AQUEOUSALKALINE MATERIAL, AND A THIRD CONDUIT FOR CONVEYING ALKALINE MATERIALFROM SAID CONSTRICTED PASSAGEWAY TO SAID REFINING VESSEL, THE SECOND ANDTHIRD CONDUITS EACH HAVING A RATIO OF LENGTH TO CROSS-SECTIONAL AREAEQUIVALENT TO A RATIO OF LENGTH TO DIAMETER OF AT LEAST 8.